import sys

from twisted.application.service import Application
from twisted.application.internet import TimerService, TCPServer
from twisted.web import server
from twisted.python import log
from twisted.cred.portal import Portal
from twisted.web.guard import HTTPAuthSessionWrapper, BasicCredentialFactory

from scrapy.utils.misc import load_object

from .interfaces import IEggStorage, IPoller, ISpiderScheduler, IEnvironment
from .eggstorage import FilesystemEggStorage
from .scheduler import SpiderScheduler
from .poller import QueuePoller
from .environ import Environment
from .config import Config
from .basicauth import PublicHTMLRealm, StringCredentialsChecker

def application(config):
    app = Application("Scrapyd")
    http_port = config.getint('http_port', 6800)
    bind_address = config.get('bind_address', '127.0.0.1')
    poll_interval = config.getfloat('poll_interval', 5)

    poller = QueuePoller(config)
    eggstorage = FilesystemEggStorage(config)
    scheduler = SpiderScheduler(config)
    environment = Environment(config)

    app.setComponent(IPoller, poller)
    app.setComponent(IEggStorage, eggstorage)
    app.setComponent(ISpiderScheduler, scheduler)
    app.setComponent(IEnvironment, environment)

    laupath = config.get('launcher', 'scrapyd.launcher.Launcher')
    laucls = load_object(laupath)
    launcher = laucls(config, app)

    timer = TimerService(poll_interval, poller.poll)

    webpath = config.get('webroot', 'scrapyd.website.Root')
    webcls = load_object(webpath)

    username = config.get('username', '')
    password = config.get('password', '')
    if username and password:
        if ':' in username:
            sys.exit("The `username` option contains illegal character ':', "
                     "check and update the configuration file of Scrapyd")
        portal = Portal(PublicHTMLRealm(webcls(config, app)),
                        [StringCredentialsChecker(username, password)])
        credential_factory = BasicCredentialFactory("Auth")
        resource = HTTPAuthSessionWrapper(portal, [credential_factory])
        log.msg("Basic authentication enabled")
    else:
        resource = webcls(config, app)
        log.msg("Basic authentication disabled as either `username` or `password` is unset")
    webservice = TCPServer(http_port, server.Site(resource), interface=bind_address)
    log.msg(format="Scrapyd web console available at http://%(bind_address)s:%(http_port)s/",
            bind_address=bind_address, http_port=http_port)

    launcher.setServiceParent(app)
    timer.setServiceParent(app)
    webservice.setServiceParent(app)

    return app
